The present invention generally relates to vibratory devices and, more particularly, to exciter mass assemblies used to generate vibrational movement in such devices.
Industrial vibratory devices, such as conveyors, feeders, and other vibrating process equipment, are generally known in the art for transporting, feeding, or otherwise processing a product. Such devices typically include a work member, such as a trough, on which rests the product to be processed. An exciter mass is resiliently connected to the trough, such as by springs. A prime mover, such as a motor having rotating shaft carrying unbalanced weights, is attached to the exciter mass. When the motor shaft rotates, the unbalanced weights create a vibratory oscillation in the exciter mass that is transferred to the trough via the springs. The vibration of the trough is, consequently, imparted to the product.
The connection between the exciter mass and the trough may be arranged to create a desired responsive movement in the product. For example, if the trough is sloped with respect to horizontal, the exciter mass may be positioned to create an entirely vertical vibration, which will allow gravity to advance the product along the trough. If the trough is horizontal, the exciter mass may be positioned to create a vibration having horizontal and vertical components to advance the product along the trough.
The resilient members used to connect the exciter to the trough are movable in a variety of motions. Springs, for example, may extend and contract in an axial direction, twist in a torsional direction, and translate in a shear direction. A given spring has a natural resonant frequency for each direction of movement. For example, rotation of the motor at the torsional spring frequency tends to move the exciter in the torsional direction. Similarly, rotation of the motor shaft at the shear and axial spring frequency tend to move the exciter in the shear and axial directions, respectively. It is desirable, however, to move the exciter in a single direction, such as in the axial direction.
Conventional vibration devices often require additional components, such as stabilizing legs, to restrict movement in the non-desired directions. In conventional vibration devices, the exciter mass is in the form of a metal slab or frame, and the motor is simply mounted to the slab or frame in a generally cantilever fashion. Consequently, as the motor shaft is rotated at different speeds, it may reach each of the spring frequencies, causing movement of the exciter mass in each of the spring directions. The use of stabilizing legs effectively raises the spring frequency in the undesired spring direction above normal motor shaft speeds, thereby minimizing or eliminating movement in the undesired spring direction. Unfortunately, the stabilizing legs add to the cost and complexity of the vibratory device.